YBa_2Cu_(3-x)M_xO_(7-δ)(M=Zn^(2+),CO^(3+))氧化物陶瓷的顺磁共振研究

EPR Study on YBa_2Cu_(3-x)M_xO_(7-δ)(M=Zn^(2+),Co^(3+))Oxide Ceramics

采用顺磁共振研究了 YBa_2Cu_(3-x)M_xO_(7-δ)(M=Zn^(2+),Co^(3+)氧化物的 EPR 谱.YBa_2Cu_3O_(7-δ)超导体室温时在 g⊥=2.05处有一微弱的顺磁信号,随 O_I 位置氧空位浓度的增加,其 EPR 信号增强,因此,可将该顺磁信号归因于 Cu 的局域 d 电子.Zn 取代 Cu 后,g⊥=2.05处的 EPR信号随取代量的提高而增强.Co 取代 Cu 后,g⊥=2.05处的信号减弱至消失,当 X=0.5时,则出现 Co 离子的顺磁信号,这些现象均可由 Cu 局域 d 电子的增加与减少来解释.

EPR spectra of YBa_2Cu_(3-x)M_xO_(7-δ)(M=Zn^(2+),Co^(3+))oxide ceramics were examined. It is shown that there is a weak EPR signal in YBa_2Cu_3O_(7-δ)superconductor,and the prin- cipal g-value is approximately g(?)=2.05.The intensity of the signal increases with in- creasing oxygen vacancy content in O_I site.Thus it can be attributed to the localized Cu d electrons.After Zn^(2+)ions substitute for Cu ions,the signal increases with increasing the Zn^(2+)dopant concentration.After Co^(3+)ions substitute for Cuions,the signal decreases with increasing the Co^(3+)dopant concentration,and finally disappears.For YBa_2Cu_(2.5)Co_(0.5)0_(7-δ)sample,the EPR signal for Co^(3+)ions appears.These phenomena can be explained by the increasing or decreasing of localized Cud electrons. Keywords:superconductor;YBaCuCoO oxide;YBaCuZnO oxide;EPR